Alternating current drop-out means for thermoelectric safety shutoff devices



Aug. 25, 1953 RB. MATTHEWS 2,649,767 ALTERNATING CURRENT DROP-OUT MEANS FOR THERMOELECTRIC SAFETY SHUTOFF' DEVICES Filed Dec. 27, 1950 53 32 K5167 fig 5Q 5676 3/ 55 L9 LGHgI 2a 2224 HI) 6 52 -63 2 26 I I &642 5 56 .1 66 Hm.

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Patented Aug. 25, 1953 ALTERNATIN G CURRENT DROP-OUT MEANS FOR THERMOELECTRIC SAFETY SHUT- OFF DEVICES Russell B. Matthews, Wauwatosa, Wis., assignor to Milwaukee Gas Specialty Company, Milwaukee, Wis, a corporation of Wisconsin Application December 27, 1950, Serial No. 202,939

13 Claims.

This invention relates, in general, to control devices, and has particular relation to alternating current drop-out means for thermoelectric safety shut-off devices.

Thermoelectric safety shut-off devices for maintaining, for example, flow of fuel to a burner as long as a thermoelectric generator is heated by the flame of a pilot burner and for shutting off the flow of fuel to the burner p extinguishment of the pilot burner flame are known in the art. These devices usually comprise an electromagnet provided with an armature connected to a controlling member, such as a valve, or an electric switch for controlling an electroresponsive valve or the like, and a thermoelectric generator adapted to be subjected, for example, to the heat of a pilot burner flame and connected in circuit with the electromagnet so that the armature is held in attracted position and the controlling member in operating position when the thermoelectric generator is heated by the pilot burner flame. Upon extinguishment of the pilot burner flame, the armature moves to retracted position with accompanying movement of the controlling member to inoperative position to shut off the flow of fuel to the burner.

Drop-out schemes for causing the thermoelectric safety shut-ofi device to drop out and shut off the flow of fuel to the burner when alternating current is applied have been previously proposed.

In John H. Thornbery and Theodore A. Wetzel Patent No. 2,340,234, patented January, 25, 1944, there is a magnet frame having a first coil connected in circuit with the thermoelectric generator and a second coil is also wound on the magnet frame and, when energized, reduces the effective magnetic attraction produced in he magnet frame by the first coil to cause h thermoelectric safety shut-off device to trip or drop out.

According to another scheme, it has been proposed to superimpose alternating current on the thermoelectric circuit to cause the thermoelectric safety shut-off device to trip or drop out.

The first-mentioned scheme requires a special electro-magnet with both the 0011 for the thermoelectric circuit and the drop-out coil on the magnet frame. As a result, if the device is desired for use without the drop-out means, such drop-out means is there, but as surplus, and without function. Moreover, these devices require terminal connectors at the thermoelectric safety shut-off device for the drop-out coil,

The second-mentioned scheme requires breaking or connecting into the thermoelectric circuit, which, where coaxial conductors are employed, presents a problem in making the desired connections. Moreover, these devices insert at least some resistance into the thermoelectric circuit, which is a factor because of the relatively minute character of the thermoelectric energy involved.

One of the main objects of the present invention is to provide an improved trip or dropout device which will not have the shortcomings of prior drop-out devices, and more particularly an improved drop-out device which does not require a magnet frame with a second coil wound thereon, or breaking or connecting into the thermoelectric circuit.

Another object of the invention is to provide a drop-out device which can be applied Where desired to a thermoelectric safety shut-off device of existing type or to thermoelectric safety shut-01f devices already in service without Winding additional coils on the magnet frames of such devices and without breaking or connecting into the thermoelectric circuit.

Another object of the invention is to provide a drop-out device comprising a coil and a magnetic frame which are adapted to be disposed in position surrounding the electromagnet of the thermoelectric device, and more particularly in position surrounding a non-magnetic body portion of the thermoelectric device within which the electromagnet is disposed, and with which magnetic flux established in the magnetic frame of the drop-out device by energization of the drop-out coil will pass through the frame of the electromagnet and reduce its effective magnetic attraction whereby to release the controlling member for operation to. safety or inoperative position.

-Another object of the invention is to provide a drop-out device comprising a coil looped about an opening, conductive means for connecting the coil in circuit with an alternating current, and a magnetic frame covering the opposite ends and outer periphery of the coil and open magnetically along the inner periphery of the coil, and with the inner peripheries of the ends of the magnetic frame directed inwardly toward the coil opening.

Further objects and advantages and numerous adaptations of the invention will appear from the following detailed description taken in connection with the accompanying drawing.

In the drawing:

Figure 1 is an axial sectional view through one form of thermoelectric safety shut-01f device, showing a drop-out device embodying the present invention applied thereto; also showing more or less schematically a thermoelectric generator for the thermoelectric device, and a pilot burner and a portion of a main burner; and

Figure 2 is an inner plan view of the drop-out device.

Referring now to the drawing, the thermoelectric device per se forms no part of the present invention, and its structure may vary widely.

The particular thermoelectric safety shut-off device selected for illustration comprises a valve body or casing I having a fuel inlet 2 and a fuel outlet 3. The inlet 2 opens into an inlet chamber 6, and the outlet 3 opens from an outlet chamber 5. Between the chambers 4 and 5 there is a wall or partition 6 provided with an opening I. An annular valve seat 8 surrounds the inlet end of the opening I, and an annular valve seat 9 surrounds the outlet end of the opening I. A pilot port or tapping I6 opens from the opening 1 between the valve seats 8 and 9 for supplying gaseous fuel to a pilot burner II through a pilot burner supply tube or pipe l2.

The pilot burner II is disposed in juxtaposition to a main burner I3 which is supplied with gaseous fuel by a pipe I 4 leading from the outlet 3. The supply of fuel to the main burner I3 may be through a mixing chamber I5 to which air is admitted, as well understood in the art.

Screwed or otherwise secured in the valve body I coaxial with the Valve seats 8 and 9 is a magnet mounting nut I6. An electromagnet I1 is enclosed within an inner shell I8 and comprises a magnet frame I9 secured, for example, to a terminal bushing 26. A coil 2| is wound around the legs of the U-shaped magnet frame I9. The bushing 26 is secured in place, for example, by screwing it at 22 into the magnet mounting nut I6 and has a threaded opening for receiving an attaching nut 23 of a thermoelectric generator lead 24.

The lead 24 comprises, for example, concentric lead conductors 25 and 26 connected in circuit at one end with concentric thermoelectric elements 21 and 28 of a thermoelectric generator 29, as more fully disclosed and claimed in Oscar J. Leins Patent No. 2,126,564, patented August 9, 1938. The thermoelectric elements 2'! and 28 are joined to form a hot thermojunction 36 which, in use, is positioned to be heated by the flame of the pilot burner II. The opposite end of the inner lead conductor 26 has a connector cone 3I which is clamped in contact with a terminal tip 32 by the nut 23. The outer tubular lead conductor 25 is connected in circuit with one side of the coil 2i through the bushing 26, and the other side of the coil '28 is connected to the inner lead conductor 26 through the terminal tip 32.

A stem 34 extends through the wall at the inner end of the shell I8, and has an armature 35 attached thereto within the shell I 8 and preferably in a manner to permit self-accommodation of the armature to the pole ends of the ma net frame I9. A safety shut-off valve member 36 is attached to the opposite end of the stem 34 within the inlet chamber 4, and preferably in a manner to permit self-accommodation of this valve member to its seat 6.

The heat of the pilot burner flame on the thermoelectric generator 29 is adapted to energize the electromagnet I'I sumciently to hold the armature 35 in attracted position and the valve member 36- in open position as long as the thermoelectric generator is heated by the flame of the pilot burner I I. When the pilot burner flame is extinguished, the armature 35 ceases to be held in attracted position by the electromagnet I7, and the valve member 36 i moved by a, coiled spring 36 into closed position engaging the valve seat 8 to shut off the flow of gaseous fuel to the main burner I3.

The heat of the flame of the pilot burner II on the hot junction or hot junctions of the thermoelectric generator 29 may not be capable of moving the armature 35 to attracted position and the valve member 36 to open position. Reset means is therefore provided for resetting or cocking the armature 35 to attracted position and the valve member 36 to open position. This reset means comprises, in general, a reset stem 46 mounted for axial movement in an opening in a reset stem mounting nut 4I screwed or otherwise secured in an opening in the valve body I. A coiled spring 42 holds the reset stem 46 in its outwardly projected position, and returns it to such position.

When the armature 35 is retracted and the valve member 36 is closed and the stem 46 is pressed inwardly, the inner end of the stem engages the valve and armature assembly and moves the valve member 36 to open position and the armature 35 to attracted position. They may be held in this position until the thermoelectric generator 29 is heated by'the flam of the pilot burner II and has energized the electromagnet I'I sufficiently to hold the armature 35 in attracted position and the valve member 36 in open position, whereupon the reset stem 46 may be released and returned to its outwardly projected position.

If desired, the reset stem 46 may be provided with a flow interrupter valve 44 for seating against the valve seat 9 to shut off the flow of fuel to the main burner I3 during the resetting operation and until the valve member 36 is held open by the electromagnet H and the reset stem 46 is released. The flow interrupter valve may, for example, be of the character more fully disclosed and claimed in Charle V. Hildebrecht Patent No. 2,114,446, patented April 19, 938. Suifice it to state that when the reset stem 46 is pressed inwardly, a coiled spring 45 moves the flow interrupter valve 44 to closed position, and the coiled spring 42 in returning the reset stem 46 to its outwardly projected position moves the valve member 44 to open position against the action of the spring 45.

The drop-out device selected for illustration comprises a coil 56 which is looped about an opening 5I and, more specifically, of toroidal or generally annular form.

The coil 56 has a magnetic frame 5| comprising magnetic end walls 52 and 53 cladding or covering the opposite ends of the coil 56, and an outer magnetic side wall 54 cladding or covering the outer periphery of the coil 56. The magnetic frame 5| is magnetically open along the inner periphery of the coil 56 and toward the opening 5|. The inner peripheral edges 55 and 55 of the magnetic end walls 52 and 53 are directed radially inwardly toward the opening 5|.

In one form of the invention the iron or magnetic walls 53 and 54 may be integral walls of an iron or magnetic cup-like structure. The other iron or magnetic end wall 52 may fit teles opi al y into the open end of this cup-like structure and over the adjacent end of the coil 50. Circumferentially spaced integral lugs 55" on the free edge of the side wall 54 of the ma netic cup are bent inwardly to secure the wall 52 in place after positioning it as shown in Figure 1. If desired, the inner periphery of the coil 50 may be covered by a brass, aluminum, plastic or other non-magnetic sleeve 56 which defines the coil opening 51, and, at the same time, leaves the magnetic frame magnetically open along the inner periphery of the coil 50.

The coil 50 and its frame are adapted to be conveniently placed in position surrounding the portion of the valve body I within which the electromagnet H is disposed by merely slipping the drop-out device into place to the position shown in Figure 1. The shell l8, and at least the portion of the valve body I thus disposed within the drop out device, are formed of suitable non-magnetic material, such as brass, aluminum, plastic or other suitable material. In one illustrative embodiment of the invention, the coil 50 has a radial dimension of about twice its depth.

The coil 50 has conductive means shown in the form of a pair of insulated conductors 58 and 59 which extend out, for example, through notches 60 in the periphery of the magnetic wall 52. Electric power for energizing the dropout winding 55 is supplied from a suitable source, for example, from line wires 6! and 62 of a suitable source of alternating current, such as a household current supply line of the type which averages about 115 volts. The lead conductors 58 and 59 of the coil 50 are connected to the line wires GI and 62 by conductors 63 and 54. One of the conductors 63-454, for example the conductor 64, has interposed therein a switch or condition responsive device 65, such as a thermostat, limit switch, manual switch or the like, for completing and interrupting the circuit for the coil 50 upon the occurrence of a predetermined condition.

For the purpose of detachably securing the drop-out device in place on the valve body I, the magnetic end wall 52 has circumferentially spaced integral lugs 68 struck up from the inner periphery thereof. Screws 59 screwed through threaded openings in these lugs 68 are adapted to be screwed inwardly to fasten the drop-out device in place on the valve body I. The dropout device is removed by merely loosening the screws 69 and slipping it from place on the valve body 5.

In use, the thermoelectric safety shut-off device functions in the usual manner. With the drop-out device applied as shown and described, the circuit for its coil 58 is normally open. When the manual switch or condition responsive means 65 is closed to complete the circuit for the dropout coil 50 while thermoelectric current is being generated at the thermoelectric generator 29 and the shut-off valve 36 is thus held open, the action is as follows:

The energization of the drop-out coil 59 by the alternating current establishes magnetic flux which flows through the magnetic walls 52, 53, and 54 of the magnetic frame. This magnetic flux passes out through one annular edge 55 or 55' of the magnetic frame, through the magnet frame IQ of the electromagnet ll, and back into the magnetic drop-out frame through the other annular edge 55 or 55, thus completing a flux path as indicated in general by the dot and dash line a in Figure 1.

The alternating current component of flux may follow the same path as the direct current component of flux established in the magnet frame 19 by the thermoelectric generator 29, but opposes the direct current flux on one cycle depending upon the character of the thermoelectric device. The drop-out device is designed to give enough effect to reduce the effective magnetic attraction of the electromagnet I! for its armature sufficiently to cause the armature 35 to be released for movement to retracted position. As a result, the valve 36 thereupon moves to closed position to shut off the flow of fuel to the main burner l3; also the flow of fuel to the pilot burner ll.

Assuming that the circuit for the drop-out coil has reopened, for example, by change from the condition which closed this circuit, then the thermoelectric device may be reset by pressing the reset stem as previously described. If the condition which closed the circuit of the drop-out coil 50 still exists and effort is made to reset the thermoelectric device, the continued energization of the drop-out coil by the alternating current will prevent the safety shut-off valve from being held open by energization of the electromagnet I! by the thermoelectric generator 29, or will cause the shut-off valve to close when the reset stem is released.

The embodiment of the invention shown in the drawing is for illustrative purposes only, and it is to be expressly understood that said drawing and the accompanying specification are not to be construed as a definition of the limits or scope of the invention, reference being had to the appended claims for that purpose.

I claim:

1. In combination, a thermoelectric device having a non-magnetic body portion within which is disposed an armature and an electromagnet comprising a first magnetic frame and first coil which when energized by a thermoelectric generator is adapted to establish magnetic flux through said first magnetic frame and said armature to hold said armature in attracted position, and a drop-out device surrounding the non-magnetic body portion of the thermoelectric device in position radially outwardly of said electromagnet, said drop-out device comprising a second magnetic frame in magnetically linked relation to said first magnetic frame and .a coil which when energized is adapted to establish in second magnetic frame magnetic flux which links said first magnetic frame through said non-magnetic body portion and is in opposition to the magnetic flux established in said first magnetic frame by energization of said first coil and sufficient to reduce the attraction of the electromagnet within said non-magnetic body portion sufficiently to release said armature from said electromagnet, said first magnetic frame and said armature within said non-magnetic body portion providing a complete magnetic flux path independent of said second magnetic frame.

2. The combination according to claim 1 wherein the coil of the drop-cut device is of generally toroidal form with a radial dimension about twice its depth.

3. In combination, an electromagnet comprising a magnet frame, a coil adapted, when energized, to establish magnetic fiux in said magnet frame, and a drop-out device comprising a, coil adapted to be energized by alternating current, and a magnetic frame for the coil of said dropout device in magnetically linked relation to the magnet frame of the electromagnet, the coil and magnetic frame of said drop-out device both surrounding the magnet frame and the coil of the electromagnet whereby, with said magnetically linked relation upon energization of the coil of the drop-out device, to establish flux in the magnetic frame of the drop-out device and through the magnet frame of the electromagnet of a character to oppose the magnetic flux established in the magnet frame of the electromagnet by its coil on one cycle of alternating current applied to the coil of the drop-out device, the coil of the first mentioned electromagnet when energized establishing magnetic flux through its magnet frame independent of the magnetic frame of the drop-out device.

4. The combination according to claim 3 wherein there is an armature adapted to be held attracted to the magnet frame of the electromagnet by the flux established in said magnet frame by the coil of the electromagnet, and wherein the flux established in the magnet frame of the electromagnet by the energization of the coil of the drop-out device is of a character to reduce the effective magnetic attraction of the electromagnet for movement of the armature to retracted position.

5. The combination according to claim 3 wherein there is an armature adapted to be held attracted to the magnet frame of the electromagnet by the flux established in said magnet frame by the coil of the electromagnet, and wherein the flux established in the magnet frame of the electromagnet by energization of the coil of the drop-out device is of a character to reduce the effective magnetic attraction of the electromagnet for movement of the armature to retracted position, and a controlling member connected to said armature to be held in operating position when the armature is held in attracted position and for movement to inoperative position upon movement of the armature to retracted position.

6. The combination according to claim 3 wherein there is a condition responsive means controlling the energization of the coil of the dropout device.

'7. In combination, a thermoelectric safety shut-off valve having a non-magnetic body portion, an electromagnet disposed within said nonmagnetic body portion and comprising a magnet frame and a coil for said magnet frame connected in circuit with a thermoelectric generator, an armature adapted to be held attracted to the magnet frame by energization of said coil by said thermoelectric generator, a valve member connected to said armature and held in open position when said armature is held in attracted position, a drop-out device comprising an annular coil surrounding the non-magnetic body portion in position radially outwardly of said electromagnet, conductive means for connecting said coil in circuit with a source of alternating current, and a magnetic frame covering the opposite ends and the outer periphery of the coil of drop-out device, the magnetic frame for the coil of the drop-out device being open magnetically to the electromagnet at the inner periphery of the drop-out device and having the inner peripheries of its ends directed radially inwardly toward the magnet frame of the electromagnet, the flux established in the magnet frame of the electromagnet by energization of the coil of the drop-out device being of a character to reduce the effective magnetic attraction of the electromagnet sufi'lciently for movement of the armature to attracted position and the valve member to open position, the flux established in the magnet frame of the electromagnet by the coil of the electromagnet being in a path independent of the magnetic frame of the dropout device.

8. The combination according to claim 7 wherein there is condition responsive means controlling the energization of the coil of the dropout device.

9. A drop-out device for application to an electromagnetic device having a non-magnetic body portion within which is disposed an armature and an electromagnet comprising a magnet frame and a coil which when energized is adapted to establish magnetic flux through said magnet frame and said armature to hold said armature in attracted position, said drop-out device comprising a channel-shaped magnetic frame of looped form adapted to be placed in position surrounding said non-magnetic body portion and a looped coil within said frame, said channel-shaped magnetic frame having a circumferential outer magnetic Wall covering the outer periphery of the looped coil and magnetic end walls covering opposite ends of said looped coil, and means for attaching the channel-shaped magnetic frame of the drop-out device to the non-magnetic body portion of the electromagnetic device with the inner edges of the end Walls thereof presented to the outer periphery of the non-magnetic body portion and magnetically linked to the magnet frame of the electromagnet within said nonmagnetic body portion to direct magnetic flux established in the channel-shaped magnetic frame by the coil of the drop-out device through said non-magnetic body portion and through the magnet frame of the electromagnet therein and in opposition to the magnetic flux established in the magnet frame of said electromagnet by energization of said first mentioned coil and sufiicient to reduce the attraction of the electromagnet within said non-magnetic body portion sufiiciently to release said armature from said electromagnet.

10. A drop-out device according to claim 9 wherein the electromagnet within the non-nagnetic body portion of the electromagnetic device comprises a coil and a magnet frame through which magnetic flux is established by the coil independent of the channel-shaped magnetic frame of the drop-out device.

11. A drop-out device according to claim 9 wherein one of the end walls of the channelshaped magnetic frame of the drop-out device is detachably secured to said magnetic frame and carries the means for attaching said channelshaped magnetic frame to the non-magnetic body portion of the electromagnetic device.

12. A drop-out device according to claim 9 wherein the inner periphery of the coil of the drop-out device is covered by a non-magnetic member. I

13. In combination, a control device having a non-magnetic body portion within which there is a first magnet frame and a first coil for establishing magnetic flux in said magnet frame and Wholly within said non-magnetic body portion, a drop-out device surrounding said non-magnetic body portion and having a second magnet frame in magnetically linked relation to said first magnet frame, and a second coil which, when energized, establishes in said second mag- 9 10 net frame and in a path which extends through References Cited in the file of this patent the non-magnetic body portion and includes said UNITED STATES PATENTS first magnet frame magnetic flux which opposes the magnetic flux established in said first magnet Number Name Date frame by said first coil, and an armature within 5 390,245 Mather 2, 1333 said non-magnetic body portion which is adapted 733,097 Waterman J 11137 7, 1903 to be linked independently of said second magnet 1,252,312 Warren Ja-IL 1, 1918 frame by magnetic flux established in said first 2,262,061 sQmers 11, 1941 magnet frame by energization of said first coil. $290,047 Hlldebrecht July 14, 1942 10 2,299,286 Wantz Oct. 20, 1942 RUSSELL T s 3 fery M May 4, 1 43 2,340,234 Thornbery Jan. 25, 1944 

